This application claims the benefit of Korean Patent Application No. 2001-31969 filed on Jun. 8, 2001, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an optical pickup device used to record information on a disk or to reproduce information from a disk, and more particularly, to an optical pickup device using an air bearing slider that can control positioning of the optical pick-up device.
2. Description of the Related Art
In general, an optical recording and/or reproducing apparatus to record and/or reproduce information to and/or from a disk, which is an optical recording medium, for example, a compact disk player (CDP) or a digital versatile disk player (DVDP), includes an optical pickup device which radiates light onto a recording surface of the disk and receives light reflected from the disk while moving in a radial direction of the disk, thereby recording and/or reproducing information to and/or from the disk. As shown in FIG. 1, a conventional optical pickup device includes a holder 8 fixed to a base 7, a bobbin 2 movably supported by elastic supports 6a through 6d whose ends are fixed to the holder 8, an objective lens 1 mounted on the bobbin 2, a focus coil 3 and tracking coils 4 installed at the bobbin 2 to drive the objective lens 1 in focusing directions xe2x80x9cAxe2x80x9d and in tracking directions xe2x80x9cBxe2x80x9d to form an electrical connection path, magnets 10 and yokes 9 generating electromagnetic forces to drive the bobbin 2 by interacting with the current flowing in the respective coils 3 and 4.
In the above-described configuration, if current is supplied to the focus coil 3, the bobbin 2 supported by the elastic supports 6a through 6d is driven in one of the focus directions xe2x80x9cAxe2x80x9d by the electromagnetic force generated by interaction between the current and the magnetic force based on the magnets 10 and the yokes 9. Thus, while controlling the current flowing through the focus coil 3, the focal distance between the recording surface of a disk (not shown) and the objective lens 1 can be controlled. Also, the bobbin 2 is driven in the tracking directions xe2x80x9cBxe2x80x9d by electromagnetic force generated by controlling current flowing through the tracking coils 4, thereby controlling the objective lens 1 to follow a desired track of the disk.
As there has recently been increasing demand for high-capacity recording media, high-density disks having small track pitches are being developed. In order to smoothly record information on and/or reproduce information from a high-density disk having a narrow track pitch, optical pickup devices tend to employ an objective lens having a high numerical aperture (NA) of 0.8 or greater. However, a drawback in employing a high-density disk and a high NA objective lens is that the focal distance between the objective lens 1 and the disk is considerably reduced to 0.2 mm or less. In other words, a high NA objective lens has a focal length of only 0.1 to 0.2 mm. In the case of employing the conventional optical pickup device shown in FIG. 1, the focal distance is so short that the objective lens 1 and the disk are liable to collide during focus control. Also, the large inertia of the bobbin 2 having the objective lens 1, the focus coil 3 and the tracking coils 4 mounted thereon limits the focusing and tracking precision of the optical pickup device shown in FIG. 1. Thus, the optical pickup device shown in FIG. 1 can be used without limitation in a system using a general disk or objective lens in which the focal distance is in the range of several millimeters, while in a system using a high-density disk or high NA objective lens in which the focal distance is in the range of 0.1 to 0.2 millimeters, the system is severely affected by inertia so that the objective lens 1 is liable to collide with the recording surface of a disk during focus control, which may cause damage to both the disk and the objective lens 1.
To solve the above-mentioned problem, there has been proposed an optical pickup device shown in FIG. 2 which is constructed such that an objective lens 22 is mounted on an air-bearing slider 21 elastically biased so as to securely contact a recording surface of a disk 23 initially by mechanical elasticity of a rotary actuator 20. If the disk 23 rotates, the air-bearing slider 21 is subjected to a lifting force so that it is lifted from the recording surface of the disk 23 and its focal position is maintained at a level where the lifting force is balanced by the elasticity of the actuator 20. Thus, in such a construction, since a gap is always maintained by air pressure formed between the slider 21 and the recording surface of the disk 23, collision of the objective lens 22 and the disk 23 never happens.
However, according to the above-described construction, since the focal position depends on the lifting force acting on the air bearing slider and the elasticity of the actuator 20, accurate focus control is not possible, lowering reliability of recording and/or reproducing.
Thus, there is a high demand for a novel optical pickup device that can overcome such problems.
Accordingly, it is an object of the present invention to provide an improved optical pickup device which can perform focus control with a high-density disk in a stable manner.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
The foregoing and other objects of the present invention are achieved by providing an optical pickup device including a slider on which an objective lens is mounted and which is elastically and movably supported by a predetermined support member, an air bearing member provided on the slider creating a lifting force to push the slider away from the disk according to air flow generated during rotation of the disc, and an actuator to change the position of the objective lens mounted on the slider in a focus direction relative to the disc.
The foregoing and other objects of the present invention may also be achieved by providing that the actuator includes a piezoelectric device installed in the slider to change the position of the objective lens by being reversibly deformed according to voltage application.